Method of manufacturing magnetic core assemblies



Sept. 7, 1965 swEENE 3,204,329

METHOD OF MANUFACTURING MAGNETIC CORE ASSEMBLIES Filed Nov. 13, 1961 2Sheets-Sheet 1 INVENTOR. JosE PH P. SWEENEY Sept. 7, 1965 J. P. SWEENEY3,204,329

METHOD OF MANUFACTURING MAGNETIC CORE ASSEMBLIES Filed Nov. 13, 1961 2Sheets-Sheet 2 ..@.@.@.@.@.@@.@@.@.@@@.@.@.@@QQQL@IQEfi- 8M i an 11?]??? INVENTOR. Jose? P. wseuw 3,204,329 METHOD OF MANUFAETURINGMAGNETIC CORE ASSEMBLIES Joseph P. Sweeney, Harrisburg, Pa, assignor toAMP Incorporated, Harrisburg, Pa. Filed Nov. 13, 1961, Ser. No. 151,797Claims. (Cl. 29-15556) This invention relates to magnetic core assemblymeans and method.

A primary object of this invention is to provide a magnetic coreassembly and a method of assembly resulting in an economy of productionof magnetic core devices.

Anotherobject of invention is to provide a magnetic core package havingcharacteristics which accommodate a continuous assembly procedureincluding core testing and wiring.

A specific object of invention is to provide a method of assembly ofmagnetic core devices wherein individual handling of cores during allphases of production is avoided.

A further object of this invention is to provide a universal coreassembly capable of use in a broad range of bit lengths and packageconfigurations.

A still further object of invention is to provide a core assemblywherein the cores and core conductors are so arranged that variousdesign applications may be accommodated without additional engineeringof core and winding placement or proximity.

Another object of invention is to provide a magnetic core assemblyadaptable to long bit lengths in a single unbroken array of cores andwindings.

Still another object of invention is to provide a core assembly whereinthe ratio of active components to packaging components is minimized.

An additional object of invention is to provide a core and windingassembly resistant to shock and vibration without the use of pottingmaterial.

The general trend toward miniaturization of electronic assembliesrelative to equipment weight, space and power requirements has resultedin production and reliability problems which substantially offset theadvantages gained through the use of solid state devices in general andmagnetic core devices in particular. Moreover, the various efforts tocounter the complexities of sub-miniaturized manufacture have developedpackaging techniques which do not lend themselves to economic productionand which produce units inherently limited as to the different space andconfiguration requirements of the equipment served by such devices. Thepresent invention contemplates a magnetic core mounting member havingcharacteristics which eliminate, to a large extent, the productionproblems of prior art devices and which provide an end product of broadutility.

The basic problem underlying both production and product in magneticcore devices is that large numbers of relatively small components mustbe combined in a manner whereby component operation will not be hamperedby field interaction between cores and windings. While much work hasbeen done with magnetic cores, the engineering of winding impedance andcore and winding proximity is, as yet, empirical and slight variationsfrequently effect substantial and unpredictable changes in operation.The present invention features a core and winding arrangement wherein avariety of equipment space and configuration specifications may beaccommodated without substantially changing core spacing and windinglength.

The magnetic core assemblies of the prior art comprising rigid panel orframe members carrying a given number of cores are representative of adesign compromise between the factors of production economy, includingac- United States Patent 0 cess to cores for wiring and the factors ofend product utility including unit size, weight, shape and functioncapability. The significant result of this compromise is that prior artdevices do not satisfy either of these requirements. As an example, theuse of rigid construction for core mounting members requires that theseparate core units be individually handled and that means be providedto move such units between the various stages of production. As afurther example, the use of rigid core mounting member requires thatideally all cores be individualy pre-tested prior to the initialassembly step. The present invention employs a flexible tape-likecomponent mounting members which may be continuously moved through allstages of magnetic core device production including core testing. Thecore mounting member of the invention thus serves the dual function ofmoving the cores through the complete manufacturing cycle, and as a coremounting means for the finished product.

The use of core mounting members of fixed dimensions, as in all knownprior art devices, has the result that when employed with equipment oflimited capability, a portion of the unit is unused or wasted and whenemployed with equipment of extensive capability, numerous units must bemechanically and electrically connected together. The present inventionfeatures a core-tape assembly which may be cut to the exact lengthneeded by equipment served.

An additional advantage of assembly of the present invention over knowndevices is that the ratio of active components such as, cores andconductors to inactive components such as supporting members and pottingmaterial is minimized from the standpoint of dimension, weight and cost.One embodiment of the present invention utilizes a tape sandwichconstruction which eliminates the use of potting material withoutincreasing the possibility of core and winding misalignment to vibrationand shock.

Other objects and attainments of the present invention will becomeapparent to those skilled in the art upon a reading of the followingdetailed description when taken in conjunction with the drawings inwhich there is shown and described an illustrative embodiment of theinven tion; it is to be understood, however, that this embodiment is notintended to be exhaustive nor limiting of the invention but is given forpurposes of illustration in order that others skilled in the art mayfully understand the invention and the principles thereof and the mannerof applying it in practical use so that they may modify it in variousforms, each as may be best suited to the conditions of a particular use.

In the drawings:

FIGURE 1 is a schematic flow diagram of the method of the inventionshowing the various necessary and possible steps of a production cycle.

FIGURE 2 is a plan view of one embodiment of the magnetic core assemblyof the invention prior to wiring.

FIGURE 3 is an enlarged section of the assembly of FIGURE 2 taken alonglines 3-3.

FIGURE 4 is a plan view of the core-tape assembly partially wired in amanner to perform a shift register function.

FIGURES 5 and 6 show two exemplary embodiments of the assembly of theinvention as employed in core packages.

As heretofore mentioned, the present invention includes a magnetic coreassembly means and method of assembly. The following description willtreat the method of assembly initially and the assembly and its variousembodiment thereafter.

Referring particularly to FIGURE 1, a plurality of successive assemblysteps are shown beginning with the tape supply and ending with eitherassembly storage or assembly cutting and storage. As will be apparentfrom the following description, certain of the steps shown may beomitted or may be performed in a non-continuous man ner with interimstorage of the core-tape member between stages. The element 20represents the tape member of the invention and comprises a thinflexible material having insulating and non-magnetizable qualities.Additionally, the tape member should be readily pierceable withoutsplitting or fracturing. Paper, Mylar, (polyethylene terephthallateresin), acetate, and glass or fiber tapes are typical materials havingthe foregoing characteristics.

The method of the invention contemplates a continuous supply of tapeprovided by means such as a reel or spool 22 motivated or drawn throughthe various method steps by means such as sprockets 40 driven at aconstant speed by any suitable means. Immediately following tape supply22 is adhesive supply 24 which may be by roller, brush or spraydepending upon the adhesive employed. As an example, if contact cementis employed, the unit 24 may comprise a roller extending the full widthof the tape member so as to apply a thin coating thereon. Alternatively,if epoxy cement is used, a narrow pressure fed brush may be employed aselement 24 to apply a strip or beading of adhesive along the tape membercenterline. The amount of adhesive employed should be only enough toassure that the cores will remain aligned on the tape until after thecore wiring step, since the core wiring being inserted through the tapewill serve to hold the cores in position thereafter.

Following the application of adhesive, the tape member 20 is moved pastcore supply 26 and cores are deposited on the tape member and securedthereto by the adhesive coating.

As shown in FIGURE 4, the tape member 116 may include sprocket slots 117by which the tape may be driven or propelled through the variousproduction steps. The slots 117 additionally serve to index the tape forproper core placement. The approximate minimum spacing between coresshould be 15 mils edge to edge. For example, when employing GeneralCeramics No. F1243- 5209, cores 196 mils Wide and of a configuration asshown in FIGURE 4, the center to center spacing would be at least 211mils. When using standard 80 mil outside diameter toroidal cores, thisdistance would be at least 95 mils. The proper initial placement of thecores on the tape member will facilitate the further steps of productionand will assure proper core and winding proximity in the end product.

The core test step follows core mounting and includes a procedurewherein the cores are tested by measuring the core switching threshold.This is accomplished by applying a magnetomotive force to the core bymeans of an input conductor or conductor inserted through the majoraperture thereof carrying a current sufiicient to first set the core;thereafter reversing the current to reset the core while measuring thevoltage induced in an output conductor threading the same aperture. Thecurrents employed should be of a quality and quantity to accomplish setand reset in a standard acceptable core with an induced voltage in theoutput conductor between maximum and minimum limits. As an example, whenusing multi-aperture cores similar to those shown in FIGURE 4, known asGeneral Ceramics Cores F12435209, the applied set pulses should be of atrapezoidal shape of an approximately 0.3 micro-second rise and falltime, 3 micro-second duration and approximately 270 milliampereamplitude. This input current pulse should produce, on the outputconductor, a voltage not more than 25 microvolts. This should befollowed by a similar set pulse of approximately 330 milliamperesamplitude with an output voltage of not less than 25 millivolts. Anynumber of voltage responsive circuits may be employed to present avisual or audible signal indicating the presence of a defective core.One simplified circuit for accomplishing this could include two switchinserted triode driven relays set to operate respectively, responsive tocore output voltage above or below the standard voltage.

With the core-tape assembly of the invention, the core test may beperformed by needle members connected to the input and output conductorsheretofore mentioned and arranged to penetrate or pierce the tapethrough the major aperture of the core and cooperate with return circuitcontacts for the conductors disposed on the underside of the tapemember.

The numeral 32 represents core removal following any test indicating thepresence of a defective core. It is contemplated that defective coresmay be removed by blade or knife means arranged to slide between thecore member and the tape. After removal of defective cores a second coresupply 36 is provided to replace the removed cores with pre-testedcores. The number of cores removed and replaced represents a smallpercentage of the total number of cores use. In view of this, theadhesive material should have a setting time at least greater than thetime required for the foregoing assembly steps.

After the step of core-resupply, the core-tape assembly may then bewired, as indicated schematically at 38, by needle means insertedthrough the core apertures and through the tape member with the variouswindings being applied in a desired pattern.

Referring now to the step indicated by numeral 50, an auxiliary tapemember 53, supplied from a reel 54, may be applied over the tape 20,cores 27 and wiring 45. Tape member 53 is generally similar inconstruction to tape member 20, but of a lighter weight and thickness.The tape member 53 should be firmly pressed against the core-tapeassembly so as to prevent core and winding movement. In addition toinsulating the cores and Windings, the tape member 53 thus serves thefunction heretofore accomplished by the application of potting material.

As shown in FIGURE 1, the final step of the method of the inventionconsists of assembly storage as by reel member 60. Alternatively, and inlarge production runs, the core-tape assembly may be cut as indicated at64 to predetermined bit lengths and stored in fiat sections 66, asshown.

As heretofore indicated, it is contemplated that the foregoing steps maybe performed sequentially and continuously. It will be apparent that asa matter of convenience, individual combinations of steps could beperformed with intermediate storage therebetween. Such intermediatestorage would follow the step of core supply or any succeeding stepthereafter.

The method of the invention may be performed by hand or by machine oralternatively, by various combinations of automatically or manuallyoperated devices. The provision of the tape slots provides a means ofcontrol assuring accurate core spacing and thereby accurate positioningfor the additional prouction steps.

In either event, the steps above described provide a unique methodwherein magnetic core devices of various sizes and shapes may beeconomically and rapidly assem bled without individual handling ofcores.

Turning now to the assembly of the invention, FIG- URE 2 represents asegment of the core-tape as it would appear after the step of coresupply 26. It will be noted that in this embodiment a row of twentymulti-aperture cores 80, separated by a space 84, is positioned on onesurface the tape member 82. The core arrangement in this embodiment isfor a ten bit shift register and the spaces 84 provide a sufficientlength of wiring (not shown) at each end of the core array to permittermination of the register conductors. For final use, the tape member82 (after wiring) would be cut at lines 86 and the core-tape assemblytherebetween would form a ten bit shift register package suitable for avariety of further packaging arrangements.

FIGURE 3 is included to show the disposition of components with coremember bedded in adhesive 88 on tape member 82. As a matter ofcomparison, the ten-bit .5 register of FIGURE 2 occupies as little asone fiftieth the volume of prior known devices of the same capability.The tape member 82, as shown in FIGURE 3, comprises in one embodimentMylar tape, 4 mils thick and 200 mils wide, as compared with a knownprior art construction of epoxy glass sheet 63 mils thick and 900 milswide.

Referring to FIGURE 4, there is shown a partially wired core-tapeassembly, manufactured in accordance with the method of the invention.Referring to US. Patent No. 2,995,731 Wiring Arrangements for ShiftRegister Employing Magnetic Cores, it will be noted that themulti-aperture cores may be connected by continuous advance and primewindings. This technique is particularly useful when employed with thepresent invention since the advance and prime windings may becontinuously threaded along the tape length in the manner indicated. Thetape member 116 may comprise any of the tape constructions heretoforedescribed. The conductor 118, which represents the drive common andnegative prime winding, is threaded through the tape 116 and thereceiving minor apertures of the cores. Conductors 120 and 122 aresimilarly threaded through tape 116 and the cores and representrespectively ADVANCE E to O and O to E in the manner explained in PatentNo. 2,995,731. With the addition of input an output windings to thereceiving aperture and transmitting aperture of the core 126 and 124 andcoupling or transfer windings between cores as described in Patent No.2,995,731, the core-tape assembly becomes a six (6) bit shift register,considerably smaller and lighter than prior art devices of the same bitcapability.

It is to be understood that in instances wherein large production runsof standardized core assembly lengths are made, the tape may bepre-punched to provide holes matching the major and minor apertureconfigurations of the particular cores employed. Additionally, thispractice may be desirable in situations wherein the number of minoraperture turns makes it difficult to thread through the tape. It will beapparent that other wiring arrangements can be utilized with thecore-tape assembly for different magnetic circuit functions.

FIGURES 5 and 6 show various applications of the present invention todifierent core arrangements. In FIG- URE 5 a wired core-tape assemblyhaving the auxiliary tape member 130, as heretofore described, is woundon a rectangular support 132 in overlapping fashion. A unit of this typemay be readily accommodated for serial to serial, serial to parallel,parallel to serial or parallel to parallel operation be individual coreconnections connected as each layer of core-tape is wrapped on thesupport 132. The individual connection may be made directly to terminals134 from each core-tape layer. The entire assembly may, if desired, bepotted or alternatively wrapped with a single insulating tape cover.

FIGURE 6 shows a further embodiment of the invention wherein the tapemember 110 is comprised of glass cloth. In this construction, the clothtape, following mounting, testing and wiring, is treated with a thincoating of epoxy or phenolic resin and placed on a mold of desiredshape. After the resin has set, the assembly may then be removed andutilized without additional support. As will be apparent, the setting ofthe resin will additionally prevent core and conductor movement due tothe threading of the core conductor 112 through the cloth material.

Changes in construction will occur to those skilled in the art andvarious apparently diflferent modifications and embodiments may be madewithout departing from the scope of the invention. The matter set forthin the foregoing description and accompanying drawings is offered by wayof illustration only. The actual scope of the in vention is intended tobe defined in the following claims when viewed in their properperspective against the prior art.

I claim:

1. A method of manufacturing magnetic core assemblies including thesteps of moving a flexible tape member through a series of productionstages; individually securing a plurality of magnetic cores having atleast one aperture therein to said flexible tape member in a pattern ofcommon orientation and spacing according to indicia thereon;individually testing each said core by inserting an input conductor andan output conductor through the said core aperture, applyingpredetermined currents to said input conductor and measuring the corevoltage induced in said output conductor against a reference voltage;removing each core having an output voltage below or above saidreference voltage and replacing each removed core with a pre-tested coreto form a continuous series of cores; wiring the said series cores byinserting conductors through an aperture therein and through the saidtape member in a pattern to effect a desired circuit function.

2. A method of assembling magnetic core devices including moving alength of flexible tape through a plurality of production stepscomprising applying an adhesive to said tape member and applying aseries of magnetic cores in a pattern of common spacing and orientationto said adhesive; testing each of said cores by measuring the voltageoutput responsive to a standard reference current input; removing eachcore having an output voltage deviating from a standard referencevoltage; replacing each removed core with a pretested core to form acontinuous series of cores; wiring said series of cores by conductorsthreaded through each core and said tape member; and applying a secondtape member over the wired core tape assembly.

3. A method of assembling magnetic core devices including the steps ofmoving a flexible tape member through a series of production stages;securing a plurality of magnetic cores to said flexible tape member in apattern of common orientation and spacing relative to spaced slotstherein; individually applying a given magnetomotive force to each saidcore and measuring the voltage produced by said core relative to astandard voltage; removing from said tape member each core having anonstandard voltage output; replacing each removed core with apre-tested core to form a continuous series of cores; inserting a numberof different conductors through said eries of cores and said tapemember; and storing the wired core-tape assembly in a single length.

4. A method of assembling magnetic core devices including the steps ofmoving a thin flexible tape member through a series of productionstages; individually securing a plurality of magnetic cores to saidflexible tape member in a pattern of common spacing and orientation;testing each of said cores by measuring the core switching threshold,removing those of said tested cores having a switching threshold aboveor below a desired value and replacing each removed core by a pre-testedcore to form a continuous series of cores; inserting conductors throughsaid series of cores and said tape in a predetermined pattern andcutting the wired core tape assembly into given lengths related to agiven circuit function.

5. A method of manufacturing magnetic core assemblies including thesteps of moving a flexible tape member through a series of assemblystages; coating the said thin flexible tape member with an adhesivematerial; depositing a series of apertured magnetic cores in a commonspaced and oriented pattern on said tape member; individually testingeach said core by measuring its switching threshold; removing each corehaving a nonstandard switching threshold and replacing each removed corewith a pre-tested core to form a continuous series of cores; insertingconductors through each said core of said series in a predeterminedpattern whereby each conductor intersects at least one core and aportion of the tape member adjacent such core; applying a further thinflexible tape member to the said series cores and conductors and to thesaid first tape member.

References Cited by the Examiner UNITED STATES PATENTS 5 7/39 Dahlgren.

8/57 Dewitz 336155 2/58 Jones.

5/59 Snyder 336-155 12/59 Damino 29-15557 10 Wohhnan.

Zack 29-155.57

Sweeney 340174 Wilk 29155.57 Clemons.

Singer 29-1555 X JOHN F. CAMPBELL, Primary Examiner.

JOHN F. BURNS, Examiner.

1. A METHOD OF MANUFACTURING MAGNETIC CORE ASSEMBLIES INCLUDING THESTEPS OF MOVING A FLEXIBLE TAPE MEMBER THROUGH A SERIES OF PRODUCTIONSTAGES; INDIVIDUALLY SECURING A PLURALITY OF MAGNETIC CORES HAVING ATLEAST ONE APERTURE THEREIN TO SAID FLEXIBLE TAPE MEMBER IN A PATTERN OFCOMMON ORIENTATION AND SPACING ACCORDING TO INDICIA THEREON;INDIVIDUALLY TESTING EACH SAID CORE BY INSERTING AN INPUT CONDUCTOR ANDAN OUTPUT CONDUCTOR THROUGH THE SAID INPUT CONDUCTOR AND MEASURING THECORE VOLTAGE INDUCED IN SAID INPUT CONDUCTOR AND MEASURING THE COREVOLTAGE INDUCED IN SAID OUTPUT CONDUCTOR AGAINST A REFERENCE VOLTAGE;REMOVING EACH CORE HAVING AN OUTPUT VOLTAGE BELOW OR ABOVE SAIDREFERENCE VOLTAGE AND REPLACING EACH REMOVED CORE WITH A PRE-TESTED CORETO FORM A CONTINUOUS SERIES OF CORES; WIRING THE SAID SERIES CORES BYINSERTING CONDUCTORS THROUGH AN APERTURE THEREIN AND THROUGH THE